Real-time computer operating systems typically supervise the execution of multiple concurrently executing applications (more precisely, applications which are repetitively scheduled and whose execution is interleaved). These real-time operating systems must provide a means for scheduling the applications. In a ‘hard’ real time operating environment such as an aircraft cockpit, applications monitoring critical functions such as radio communication data and navigation information are typically executed together with applications monitoring other less critical functions. An operating system which supervises these multiple applications must ensure that the applications monitoring the less critical functions do not prevent the higher criticality applications from executing in a timely manner. In such an environment the computer operating system application scheduler must accomplish this by providing some form of time partitioning between the applications.
Presently available operating systems do not accurately account for operating system overheads such as interrupt handling, and are therefore incapable of enforcing timing boundaries between the applications. This lack of capability arises because existing Rate Monotonic Analysis (RMA) and Rate Monotonic Scheduling (RMS) theory and practice fail to account for computer operating system overheads and processor interrupts when determining the feasibility of a proposed schedule.